Technical Field
The present invention relates to a method for synthesizing multi-wall carbon nanotubes utilizing atomization in an injection vertical chemical vapor deposition reactor.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
In the last decade, extensive studies have been conducted on the synthesis of carbon nanotubes (CNT). Different paths of formation and precursors result in a variety of carbon nanomaterials of numerous shapes and sizes. See N. M. Mubarak, E. C. Abdullah, N. S. Jayakumar, and J. N. Sahu, “An overview on methods for the production of carbon nanotubes,” J. Ind. Eng. Chem., vol. 20, no. 4, pp. 1186-1197, July 2014; and H. Golnabi, “Carbon nanotube research developments in terms of published papers and patents, synthesis and production,” Sci. Iran., vol. 19, no. 6, pp. 2012-2022, December 2012, each incorporated herein by reference in their entirety.
By tuning reaction specifications, one can produce single wall or multi-wall CNT. CNT can be produced in large quantity by three basic methods: arc discharge, laser ablation and chemical vapor deposition (CVD) methods. See A. Shaikjee and N. J. Coville, “The role of the hydrocarbon source on the growth of carbon materials,” Carbon N.Y., vol. 50, no. 10, pp. 3376-3398, August 2012, incorporated herein by reference in its entirety. Among these three, modifications of CVD reactors have led to flexible and economical methods and these properties make CVD reactors an exceptional choice for, not only research purposes, but also for commercial applications with large scale reactors. See M. Paradise and T. Goswami, “Carbon nanotubes—Production and industrial applications,” Mater. Des., vol. 28, no. 5, pp. 1477-1489, January 2007; P. M. Ajayan, “Nanotubes from Carbon,” Chem. Rev., vol. 99, no. 7, pp. 1787-1800, July 1999; and A. Mamalis, L. O. Vogtländer, and A. Markopoulos, “Nanotechnology and nanostructured materials: trends in carbon nanotubes,” Precis. Eng., vol. 28, no. 1, pp. 16-30, January 2004, each incorporated herein by reference in their entirety.
A typical CVD reactor consists of two main parts in a horizontal assembly: a preheating zone and a reaction zone. A feed precursor, in solution form, enters from the preheating zone along with reaction gas and after vaporization; carrier gas takes the vapors to reaction zone, where reaction occurs. See R. Andrews, D. Jacques, A. M. Rao, F. Derbyshire, D. Qian, X. Fan, E. C. Dickey, and J. Chen, “Continuous production of aligned carbon nanotubes: a step closer to commercial realization,” Chem. Phys. Lett., vol. 303, no. 5-6, pp. 467-474, April 1999; Y. Cheol-jin, Lee; Jae-eun, “Mass synthesis method of high purity carbon nanotubes vertically aligned over large-size substrate using thermal chemical vapor deposition,” U.S. Pat. No. 6,350,488 B1, 2002; A. Cao, L. Ci, G. Wu, B. Wei, C. Xu, J. Liang, and D. Wu, “An effective way to lower catalyst content in well-aligned carbon nanotube films,” Carbon N.Y., vol. 39, no. 1, pp. 152-155, January 2001; S. Huang, “Substrate-supported aligned carbon nanotube films,” U.S. Pat. No. 7,799,163 B1, 2010; and R. Andrews, D. Jacques, D. Qian, and T. Rantell, “Multiwall Carbon Nanotubes: Synthesis and Application,” Acc. Chem. Res., vol. 35, no. 12, pp. 1008-1017, December 2002, each incorporated herein by reference in their entirety. Otherwise solid precursor is put in a boat, which is placed in the preheating zone and after the precursor is vaporized then the carrier gas takes it to the reaction zone. The reactor works as a batch reactor and normally is used for research purposes. See M. H. Rümmeli, A. Bachmatiuk, F. Börrnert, F. Schäffel, I. Ibrahim, K. Cendrowski, G. Simha-Martynkova, D. Piacá, E. Borowiak-Palen, G. Cuniberti, and B. Buchner, “Synthesis of carbon nanotubes with and without catalyst particles.,” Nanoscale Res. Lett., vol. 6, no. 1, p. 303, January 2011; A. M. Cassell, J. a. Raymakers, J. Kong, and H. Dai, “Large Scale CVD Synthesis of Single-Walled Carbon Nanotubes,” J. Phys. Chem. B, vol. 103, no. 31, pp. 6484-6492, August 1999; N. Lee and S. Kr, “Method of vertically aligning carbon nanotubes on substrates at low pressure using thermal chemical vapor deposition with DC bias,” U.S. Pat. No. 6,673,392 B2, 2004; F. Danafar, a. Fakhru'l-Razi, M. A. M. Salleh, and D. R. A. Biak, “Fluidized bed catalytic chemical vapor deposition synthesis of carbon nanotubes—A review,” Chem. Eng. J., vol. 155, no. 1-2, pp. 37-48, December 2009; and H. Hou, A. K. Schaper, F. Weller, and A. Greiner, “Carbon Nanotubes and Spheres Produced by Modified Ferrocene Pyrolysis,” no. 24, pp. 3990-3994, 2002, each incorporated herein by reference in their entirety.
For solid-gas interactions, a vertical CVD reactor is used. Solid precursor is continuously fed from the upper region of the reactor, where, after preheating, it enters into the reaction zone. Carrier gas is introduced from bottom of the reactor to fluidize the solid precursor and the reaction gas provides a reduced environment to accelerate the reaction. CNT form in the reaction zone and due to its low density, the carrier gas takes unreacted fluidized solid precursor out from the top of the reactor. However, there are features like bed height, pressure drop, fluidization velocity, product purity, reaction time control that make this system difficult to handle and to operate. See D. Venegoni, P. Serp, R. Feurer, Y. Kihn, C. Vahlas, and P. Kalck, “Parametric study for the growth of carbon nanotubes by catalytic chemical vapor deposition in a fluidized bed reactor,” Carbon N.Y., vol. 40, pp. 1799-1807, 2002; Q. Weizhong, L. Tang, W. Zhanwen, W. Fei, L. Zhifei, L. Guohua, and L. Yongdan, “Production of hydrogen and carbon nanotubes from methane decomposition in a two-stage fluidized bed reactor,” Appl. Catal. A Gen., vol. 260, no. 2, pp. 223-228, April 2004; Y. Yen, M. Huang, and F. Lin, “Synthesize carbon nanotubes by a novel method using chemical vapor deposition-fluidized bed reactor from solid-stated polymers,” Diam. Relat. Mater., vol. 17, no. 3, pp. 567-570, 2008; Q. Weizhong, W. Fei, W. Zhanwen, L. Tang, Y. Hao, L. Guohua, and X. Lan, “Production of Carbon Nanotubes in a Packed Bed and a Fluidized Bed,” AIChE, vol. 49, no. 3, pp. 619-625, 2003; F. Wei, Q. Zhang, W. Qian, H. Yu, Y. Wang, G. Luo, G. Xu, and D. Wang, “The mass production of carbon nanotubes using a nano-agglomerate fluidized bed reactor: A multiscale space-time analysis,” Powder Technol., vol. 183, pp. 10-20, 2008; Y. Hao, Z. Qunfeng, W. Fei, Q. Weizhong, and L. Guohua, “Agglomerated CNTs synthesized in a fluidized bed reactor: Agglomerate structure and formation mechanism,” Carbon N.Y., vol. 41, pp. 2855-2863, 2003; C. Hsieh, Y. Lin, W. Chen, and J. Wei, “Parameter setting on growth of carbon nanotubes over transition metal/alumina catalysts in a fluidized bed reactor,” Powder Technol., vol. 192, no. 1, pp. 16-22, 2009; Y. Wang, F. Wei, G. Luo, H. Yu, and G. Gu, “The large-scale production of carbon nanotubes in a nano-agglomerate fluidized-bed reactor,” Chem. Phys. Lett., vol. 364, no. 5-6, pp. 568-572, October 2002, each incorporated herein by reference in their entirety.
Injection vertical CVD (IVCVD) for a liquid feed system is a modified process that has not been reported previously for CNT synthesis. The precursor solution is injected from top into the reactor by a new technique, an “ultrasonic atomization system.” The ultrasonic atomization system increases the surface area of the precursor prior to entering the preheating zone. See A. H. Lefebvre, Atomization and Sprays p. 434, incorporated herein by reference in its entirety. Reaction gas along with carrier gas take feed droplets into the reaction zone where CNT forms. Exhaust gases leave from the bottom of the reactor. By using this technique the efficiency of the reactor is increased. Another advantage of using IVCVD reactor is that it operates at low pressure as no fluidization velocity is required to be maintained. See Q. Zhang, M.-Q. Zhao, J.-Q. Huang, Y. Liu, Y. Wang, W.-Z. Qian, and F. Wei, “Vertically aligned carbon nanotube arrays grown on a lamellar catalyst by fluidized bed catalytic chemical vapor deposition,” Carbon N.Y., vol. 47, no. 11, pp. 2600-2610, September 2009, incorporated herein by reference in its entirety.
There are different types of atomizer nozzles that can be used combined with an ultrasonic generator, like: narrow spray, wide spray with or without extension, radial spray and extra-long atomizer nozzle. See “Ultrasonic Atomizer Spray Nozzle Technology.” Available from Sonozap Corp of Farmingdale, N.Y., USA, incorporated herein by reference in its entirety.
Aromatic solvents like benzene, toluene, xylene, and phenol are usually used as a carbon source for multi wall CNTs synthesis. Organometallocenes are often used as a catalyst. See N. Koprinarov, M. Konstantinova, T. Ruskov, and I. Spirov, “Ferromagnetic Nanomaterials Obtained by Thermal Decomposition of Ferrocene in a Closed Chamber,” Phys, vol. 34, pp. 17-32, 2007, incorporated herein by reference in its entirety. Ferrocene is non carcinogenic and is preferred for large scale production of CNT over other organometalic compounds (such as nickelocene). See O. Smiljanic, B. L. Stansfield, J.-P. Dodelet, A. Serventi, and S. Désilets, “Gas-phase synthesis of SWNT by an atmospheric pressure plasma jet,” Chem. Phys. Lett., vol. 356, no. 3-4, pp. 189-193, April 2002, incorporated herein by reference in its entirety.
In view of the forgoing the object of the present disclosure is to provide a method for preparing CNT using an ultrasonic atomization system and a vertical chemical vapor deposition reactor.